17
20
19
18
GND
16
CH.2 IN B
CH.3 IN B
15
I 2C-A0
SDA
VS+ 11
14
13
12
SCL
CH. 3 SAG
I 2C-A1
CH.1 IN B
CH.2 IN A
CH.3 IN A
CH.1 IN A
NC
CH.3 OUT
CH. 2 SAG
CH.2 OUT
CH. 1 SAG
CH.1 OUT
NC
1
2
3
4
5
6
7
8
9
10
+
S-Video
Y’
S-Video
C’
CVBS
Y’
P’B
P’R
R
DAC /
Encoder
3.3V
75 W
Video
Out1
Video
Out2
Video
Out3
0.01 F
m
+Vs
100 F
m
330 F
m
(SeeNote A)
330 F
m
(SeeNote A)
330 F
m
(SeeNote A)
I C
Controller
2
DC+135mV
SLOS479B
– OCTOBER 2005 – REVISED MARCH 2011
The I2C interface of the THS7303 allows each channel to be configured totally independent of the other
channels. One of the benefits is that a multiple output encoder (or DAC) can be routed through one THS7303
with the proper input configuration and low-pass filter required regardless of the signal. This is useful for a
portable system or in a low-cost system where only one set (or two sets in parallel) is desired on the output of
the system. An update of the I2C commands changes the THS7303 channels. An example is shown in Figure 69 where the input MUX allows for one set of HDTV signals to be put into the THS7303, and then through an I2C
update, a SDTV set of signals is sent through the THS7303 with the proper input mode and low-pass filters.
A.
Due to the high frequency content of the video signal, it is recommended, but not required, to add a 0.01-
μF capacitor
in parallel with these large capacitors.
Figure 69. Typical SD/ED/ and HD Video and SDTB Encoder DAC Driving a Single THS7303
Although the circuit of
Figure 69 conserves space and cost, the reuse of the output connections may not be the
best solution. For a complete 6-channel system, it is better to use the THS7303 and the THS7313 (see
SLOS483) together, as shown in
Figure 70. The THS7313 is targeted for SDTV signals and is limited to an
8-MHz filter. As discussed in the I2C section, it is easy to have both parts in one system because the I2C address
of each part can be one of four discrete addresses by the logic appearing on the I2C-A1 and I2C-A0 lines.
Copyright
2005–2011, Texas Instruments Incorporated
35